Table 2 Methods for detecting parasites in snails

Tanzania

Bulinus globosus and Bu. nasutus

Conventional and nucleic-acid amplification diagnostics (cercarial shedding and real-time PCR DraI)

The PCR approach makes it possible to detect pre-patent infections, unlike cercarial excretion, which shows infection only when the cercariae have matured

Although PCR detects pre-patent infections, these often do not develop to patency. This may be due to host-parasite incompatibility and/or snail longevity. This PCR is non-specific and detects a group of parasites

[76]

Sudan

Bi. pfeifferi, Bu. truncatus, Bu. forskalli, Cleopatra bulimoides, M. tuberculata, Physa acuta, and Lymnaea natalensis

Conventional diagnostics (cercarial shedding test)

The excretion of cercariae and the use of morphological characteristics to identify associated trematodes are less costly than the use of molecular techniques, but more suitable for use in the field. They can also be used to assess a snail’s ability to transmit a parasite

The use of cercarial excretion and morphological characteristics to identify snails and the trematodes associated with them is not precise and is often limited to the genus, unlike more reliable molecular techniques

[58]

Tchad

Bu. truncatus, Bu. forskalii, and Bi. pfeifferi

[27]

Ethiopia

Bi. pfeifferi, Bi. sudanica, B. globosus, Bu. forskalii, and Lymnaea natalensis

[48]

Egypt

Bi. alexandrina

Conventional and nucleic-acid amplification diagnostic methods (cercarial shedding and snail crushing) and PCR

PCR had an average 100% sensitivity and specificity. PCR techniques could detect preclinical or latent infection

The cost of reagents needed for PCR is relatively high when compared to conventional methods. PCR methods require skilled and trained technicians

[77]

Tanzania

Biomphalaria sp

Nucleic-acid amplification diagnostics (real-time PCR)

More sensitive for detecting infections than cercarial excretion. Faster and allows better assessment of infection rates

The technique is expensive and cannot be used directly in field settings for routine assessment of infection in snails. Further testing is required to rule out cross-reactions with other trematodes

[78]

Egypt

Bu. truncatus and Bi. alexandrina

Conventional and nucleic-acid amplification diagnostic (microscopic techniques (cercarial shedding, snail crushing) and PCR)

PCR is more sensitive for detecting infections than conventional techniques. Conventional techniques only detect parasites when they are mature. PCR detects them earlier and is a potential tool that can be used to monitor schistosome transmission on a large scale. However, there are disadvantages of using PCR in the field

The results obtained when conventional techniques are used to detect infection are underestimated because they only detect the mature stages of the parasite. Although PCR has a higher sensitivity than conventional techniques, there are cases of inaccurate detection

[37]